Hmmm,
Long, long ago in a galaxy far far away, I worked in the oil and gas industry.
One part was the construction of gas and oil treatment facilities as
well as pipelines.
The process was that I would weld together segments of pipeline or
tanks and the hydrotest them.
In that case hydrotesting involved filling them with water at very
high pressures, sealing it and monitoring the pressure for any loss.
Why water? Because it only leaks, it doesn't explode the pipeline or tank.

Jerry H.

At 03:28 PM 10/20/2010, you wrote:
>State of Maine has the same three-year requirement for "hydrotesting"
>them. They'll get stamped with a four digit number of the form MMYY.
>
>Hydrotesting is just fancy for sticking it upside down deep into a
>water bath, and investigating for any bubbles forming near the
>nozzle and valves over a set amount of time.
>
>There is a limit on how many times the tanks can be hydrotested
>though, I think it's 10 times?
>
>Those of you at the Michigan meeting may have seen how ours
>were modified by Roger Feeley, with a short curve of pipe off
>the sawed off diffuser, so that the jet is nowhere near your
>hand on the handle. That makes ours much safer for using
>on the rotating platforms--although I did scare some people
>who didn't know I had a modified tank.
>
>My fire extinguisher cart here, which I also brought to
>Michigan was built following the straightforward design of
>the Red Ball Express at Brown, and the Maiullo Rutgers model
>(but without the "sail" board which I want to retrofit onto ours.)
>
>There probably is video out there somewhere with the
>Dave & David "race" from summer 2009.
>
>David
>
>tap-l@lists.ncsu.edu writes:
> > Sammie,
> >Right you are, and it's every three years.....
> >Dave
>
>**31st Annual UMaine Physics Meeting: March 11-12, 2011
>====================================================
>David E G Sturm - sturmde@maine.edu - 1.207.581.1241
>--Physics & Astronomy Instructional Laboratories
>--Bennett Hall Lecture Demonstration Facilities
>--Mainely Physics Road Show --PIRA Past President '09-'10
>Dept of Physics & Astronomy -- University of Maine
>5709 Bennett Hall -- Orono ME 04469-5709
>http://www.physics.umaine.edu/
>=============================================